The invention relates generally to endoprosthesis and, more specifically, to a stent graft device for delivery to an area of a body lumen that has been weakened by damage or disease, such as an aneurysm of the abdominal aorta. Several areas of the body are particularly suitable for receiving an endoprosthesis, commonly referred to as an intraluminal stent to hold open and insure the patency of a body lumen. Two such areas include the coronary arteries and the aorta, especially in the area where an aneurysm has developed.
An abdominal aortic aneurysm (“AAA”) is an abnormal dilation of the arterial wall of the aorta in the region of the aorta that passes through the abdominal cavity. The condition most commonly results from atherosclerotic disease. Frequently, abdominal aortic aneurysms are dissecting aneurysms, that is aneurysms that are formed when there is a tear or fissure in the arterial lining or wall through which blood is forced and eventually clots, forming a thrombosis which swells and weakens the vessel. Abdominal aortic aneurysms do not cause pain, but can be detected in a thorough physical examination. If the aneurysm is not detected and treated, it is likely to rupture and cause massive hemorrhaging fatal to the patient.
AAAs have been traditionally treated by some form of arterial reconstructive surgery which commonly is referred to as a “triple-A” procedure. One such method is by-pass surgery, in which an incision is made into the abdominal cavity, the aorta is closed off above and below the site of the aneurysm, the aneurysm is resected, and a synthetic graft or tube sized to approximate the diameter of the normal aorta is sutured to the vessel to replace the aneurysm and to allow blood flow through the aorta to be reestablished. The graft commonly is fabricated of a biocompatible material that is compliant and thin-walled. Nylons and synthetic fibers such as those manufactured under the trademarks DACRON or TEFLON have been found to be suitable for the construction of the graft. Studies have shown that the mortality rate associated with this surgical procedure is favorable (less than 5%) when it is performed prior to rupture of an aneurysm. However, patients having an AAA typically are over 65 years of age, and often have other chronic illnesses which increase the risk of perioperative or post-operative complications. Those patients thus are not ideal candidates for this type of major surgery. Further, it has been pointed out that this procedure is not often successfully resorted to after an aneurysm has ruptured (the mortality rate increases to over 65%) because of the extensiveness of the surgery and the time required to prepare a patient for it.
Because of the aforementioned disadvantages to conventional surgical methods, another procedure was developed as an alternative to conventional, major surgery. This method also involves emplacement of a graft at the site of the aneurysm; however, the graft is deployed there by being routed through the vascular system carried by a catheter, wire or other device suitable for negotiating the vasculature.
More recently, grafts have been used in combination with stents, wherein the apexes of the stents are aligned circumferentially when the stent is crimped which may increase the overall delivery profile. There is an ongoing need for lower profile stents-grafts for treating AAA in order to better treat patients less invasively.